g0301_0400.s0303_range_sum_query_immutable.NumArray Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0301_0400.s0303_range_sum_query_immutable;

// #Easy #Array #Design #Prefix_Sum #Programming_Skills_I_Day_12_Class_and_Object
// #2022_07_07_Time_7_ms_(100.00%)_Space_44.9_MB_(96.34%)

public class NumArray {
    private int[] sums;

    public NumArray(int[] nums) {
        sums = new int[nums.length];
        for (int i = 0; i < nums.length; i++) {
            if (i == 0) {
                sums[i] = nums[i];
            } else {
                sums[i] = sums[i - 1] + nums[i];
            }
        }
    }

    public int sumRange(int i, int j) {
        if (i == 0) {
            return sums[j];
        }
        return sums[j] - sums[i - 1];
    }
}

/*
 * Your NumArray object will be instantiated and called as such:
 * NumArray obj = new NumArray(nums);
 * int param_1 = obj.sumRange(left,right);
 */